Go to https://openrouteservice.org/dev/#/login, then you need to create an account to get the free API key (you can also use your GitHub Account) .
After singing up, you will be redirected to the dashboard and need to input some credentials for your account. Then you can now access the TOKENS beside the PROFILE tab.
Last is, you need to create a token in the TOKEN tab, then set it into free and also put a name for it. After that you can now see and copy your generated API key on your Openrouteservice account.